ILX Mesoscale Discussion

GOES_East Mesosector 2 Imagery (Band 2)

The effective surface cold front remains well north of Illinois, draped west to east across central Wisconsin as of the 22z surface analysis. Further south across the state, two main forcing mechanisms continue to play host to strong to severe convection. The first (southernmost boundary) is nearly stationary acting as the area of primary convergence, while also service as the dividing line between 70 degree dewpoints (south) and mid to upper 60s (north). The second is an outflow boundary loosely associated with earlier day convection, which continues to race southward driven largely by cold pool propagation. This boundary is anticipated to overtake the primary boundary over the next few hours, ushering the majority of shower and storm activity south of the Lincoln IL CWA later this evening (Showcased well by NUCAPS forecasts). With ample CAPE (1500 - 2500 J/KG per the 22z AllSkyLAP product) remaining along and south of said boundaries, storms are expected to retain their intensities through the early evening hours. Primary threats will remain damaging wind gusts, large hail, and flash flooding primarily in areas that see repeat thunderstorm convection this afternoon and evening.

-----------------------------------------------------------------------------------------------------Mountain Bone

Lots of lightning in northwest CWA

Highest FED and bright TOE...



...for the cell in Monroe County MO.  Cell is not that tall however, and ProbSevere is not too excited about it yet.

Charley

Line Running Into Drier Air?

IR and RGB imagery showing outflow coming out of the storms in the eastern LSX area not firing up additional storms.  NUCAPS 400-200 mb RH product shows quite a bit of drier air that the line is pushing into.  More moisture is west of the MO/IL line, so that part of the line may have a better chance to maintain themselves/develop new cores ahead of the line along that outflow.

Charley

Mesoscale Update

Band of storms dropping in from the north is moving into an environment favorable to at least maintain severe wind gusts as well as some hail potential.  AllSky CAPE parameter shows the line moving into airmass with 2500 J/kg, similar to values given by earlier ILX special sounding and recent modified NUCAPS sounding.  Latest RAP shows DCAPEs up to 1400 J/kg, indicating good potential for severe wind gusts. Had a couple of reports of blackout conditions from blowing field dirt along I-55 near Litchfield.

Charley

Comparing Operational Derived Products

Total PW looks good from the operational version (minus the blacked out data, of course).  It is a little blotchy on the merged TPW (left).  A similar comparison below of the AllSky TPW and Operational product.



CAPE is a different story.



AllSky calculations are mostly in a clear airmass, as you can tell by the operational product not being blacked out.  Peak values on the right are in the 1700-1800 J/kg range, whereas points on the left peak at 2600-2800.

Charley

Another rise in mid-level moisture on AllSky Layered PW

Similar to MPX area yesterday, the 0.9-0.7 sigma level LPW product had an area ahead of the line of storms that had increasing moisture.

Similar Soundings

Modified NUCAPS sounding near ILX is pretty similar to KILX special sounding taken at 17Z!  MUCAPES both around 3000 and LI -9.
Values similar to AllSky at 18Z.




Those CAPE values near 2500 J/kg...also similar.
This similarity gives us some confidence in new forecasts, especially in clear sky regions out ahead in the AllSky data.
The forecast NUCAPS CAPE does not show much to the south of our line...and based on clear skies and warm conditions to the south would tend to lean away from this forecast.



Charley

Springfield Illinois Storms

Right now I'm analyzing the various new products to nowcast where and when storms will intensify. Currently I'm comparing ALLsky cape to the mesoanalysis from the spc. Right now the mesoanalysis is higher with cape compared to allsky. Over our area the it's cloudy so the it's taking data from the GFS.

A cell in our western counties ramped up very quickly while our computers were down. Prob severe immediately directed our eye to the cell. The probsevere lined  up with an uptick in vil values and the threat for damaging winds



I'm comparing the actual sounding to what's shown on nucaps, and allsky. Trying to see what's initializing the best. The actualy sounding shows 3000kj of cape around 17z.



Around the same time allsky shows a similar value of cape.



Here's what the modified and unmodified nucaps are showing.
I'm also looking at GLM products to see trends with convection. The combination of event density and glm minimum flash area help me to see the rapidly growing updrafts as well as cell that are producing hail. That's the case right now. My warned cell is producing penny size hail.

NUCAPS Forecast showing increasing CAPE in the south

The gridded NUCAPS forecast indicates higher CAPE values moving east into the southern IND area the next few hours. Will be expecting severe thunderstorms to develop later today.

ILX Upper-Air Sounding comparison to NUCAPS and Modified NUCAPS

Above is a special sounding released by the ILX office around 17z on June 5th, 2019. Below is the output for the NUCAPS and sequential Modified NUCAPS sounding from around the same time and as close to the same area as possible.



The NUCAPS pass pictured above was primarily in a cloud-free environment behind an old outflow boundary to its south and ahead of a developing line of convection to its north. Visually, it tended to underdue the CAPE values in the environment, especially in the low to mid levels.



The modified NUCAPS sounding (above) did show some skill in incorporating more accurate boundary layer conditions, which in turn, upped the CAPE values considerably (almost 2x in some cases). This brought the values into better agreement to the in-situ observation from NWS ILX with the exception of the SFC based CAPE which remained considerably underdone.
---------------------------------------------------------------------------------------------------Mountain Bone